Polycrystalline ZnO:Al thin films have been prepared by the (Sol-gel) chemical deposition method. The ZnO:Al thin films are very transparent (similar to 90%) in the near UV, VIS and IR regions. The films are oriented along the c-axis ([0 0 2] direction) in the hexagonal structure. It is known that pure ZnO thin films are not chemically stable in corrosive media, but aluminium stabilizes the ZnO system and increases its electrical conductivity. Finally, the ZnO:Al thin films are reasonably stable under storage in air and in reactive atmospheres like O-2, H2O, H-2 or in weak acids. Dark-and photo-conductivity of the ZnO:Al films are very high (1-100 Ohm(-1) cm(-1)), so that they can be used as transparent conductors in solar cells or in electrochromic devices.